Currently, most commercially available edible coatings utilize a synthetic cellulosic polymer such as hydroxypropylmethylcellulose (HPMC). Other synthetic film-formers, which are commonly used, include ethylcellulose, methylcellulose, polyvinylpyrrolidone, and polydextrose. The foregoing are usually used in combination with other ingredients including fillers, for example, lactose or maltodextrin; plasticizers, such as polyethylene glycols, dibutyl sebacate, and triethyl citrate; surfactants; and often coloring materials such as a food dye or pigment, including opacifiers such as titanium dioxide and the like. A particular disadvantage of coatings based primarily on HPMC is that the coating may harden over time and therefore increase tablet disintegration times. An increase in disintegration time delays the bioavailability of the active ingredient at least in proportion to the increase in disintegration time. Many other agents commonly used in coating compositions are also known to delay release of pharmaceutical agents, such as enteric coatings which use polymeric film forming materials which are insoluble in water, or gastric fluid some of these being specifically selected to by-pass both the stomach and small intestine and provide colonic release.
U.S. Pat. No. 6,267,808 discloses bright white film-coating compositions, which are dextrose based, and comprise an auxiliary film-former. The primary film-former of the invention claimed is dextrose. The auxiliary film-former may belong to a diverse class of agents such as PVP, HPMC, and dextrin's modified starches, gums, alginates, lactose, tapoica and PVA. The function of the auxiliary film-former is to enhance the strength of the film-coat by preventing the cracking of the primary film coat and to prevent edge wear/chipping of the coated substrate.
U.S. Pat. No. 6,274,162 describes elegant film coating systems comprising a primary film former, the primary film former comprising low bloom strength gelatin, or hydroxyethyl cellulose, or a combination thereof and a secondary film former, or a plasticizer, or a surfactant, or a glidant, or a suspension aid, or a colorant, or a flavorant, or a combination thereof. The secondary film former maybe sodium alginate, sodium carboxymethlylcellulose, pectin, gelatin, propylene glycol alginate, metlhylcellitlose, polydextrose, or combinations thereof.
U.S. Pat. No. 6,468,561 describes coatings comprising a polydextrose as a primary film-former and a secondary film-former comprising sodium alginate or propylene glycol alginate. The advantages of using a polydextrose based coating include the excellent film coat obtained possessing excellent adhesive qualities coupled with good organoleptic properties, that are low calorie and non-cariogenic in nature.
In the preparation of a coating formulation to be sprayed, the film former is usually dissolved or dispersed in a solvent, for example, water, along with the other ingredients of the formulation. In aqueous systems, since many polymers require significant time to become fully hydrated, the coating formulation must frequently be prepared in advance of the time it is to be applied to the tablets. A common procedure is to prepare these coating formulations the day preceding the coating operation in order to assure adequate hydration of the polymers used in them. In this present invention it is eventually found that polymer hydration required is as low as quarter an hour only.
The coatings of this invention meet U.S. Pharmacopoeia standards for rapid or immediate dissolution (U.S.P. monograph 23) of active ingredients from tablets or other solid dosage forms coated with them. They provide prompt release or dissolution consistent with the release rates, which is normally obtained with the uncoated tablets or other substrates. Thus, they do not adversely impact or retard release of active ingredients from a substrate coated with them. Further, the coatings of this invention are readily dispersed and rapidly hydrated in aqueous media for application to a coating substrate, and provide elegant coatings which have all the benefits of coatings now in commercial use without the drawbacks that are common to them.
It is a common practice to coat pharmaceutical and veterinary tablets to obtain several advantages. Among these are to mask unpleasant tasting active ingredients with a barrier coat, to improve the surface characteristics of tablets to make them easier to swallow, to reduce the absorption of water or moisture which can potentially degrade the active ingredient or promote some other undesirable change in the tablet structure, and simply to make a more elegant appearing tablet.
Another very important function of a pharmaceutical or veterinary tablet coating is to improve the integrity of the tablet itself. Uncoated tablets are often subject to being abraded or chipped, causing a loss of active ingredient in the process. More dramatically, they may break into two or more pieces. One measure of a useful coating is its ability to prevent any of these physical degradations of tablet structure. The effectiveness of a coating material to prevent abrading, chipping, or breakage of the tablet is determined by friability testing.
Confectionery and foods may be coated with a formulation to preserve the confection or food from deteriorating by contact with the oxygen and the moisture in the atmosphere. Coats can provide improved appearance and desirable organoleptic properties to the food as well as preventing loss of flavor.
Animal feed may be coated to improve its flowability, appearance and its resistance to powdering or dusting. In such applications, the coating may be formulated to include vitas, hormones, antibiotics, or the like, to benefit the livestock, which will consume the feed.
Seeds may be coated to preserve the viability of the seeds by protecting against moisture. They may also be coated as a means for increasing particle size to facilitate mechanical planting. A dye can be included in the coating formulation to identify the seeds as to quality, type, or some other designation. Frequently, a pesticide, e.g., a fungicide, is incorporated into the coating formulation to protect both the seed itself and the seedling that results from germination of the seed. In all cases, this coating must not decrease the viability of the seeds or interfere with germination when the seeds are planted in the soil.
Fertilizers, in either granular or tableted forms, may be coated to retain the integrity of the form and, especially, to protect the fertilizer from moisture, which can cause agglomerates during storage, which could make rapid, even application to the soil difficult or inconvenient.
Coating of tableted pesticide formulations serves to maintain the integrity of the tablets or granules until they are placed in water where they rapidly disintegrate, forming a solution or slurry to be applied to the soil or plants. A second, and equally important, function of the coatings on tablets containing pesticides is to prevent human contact with the pesticide, thereby increasing safety for those handling and applying the pesticide.